* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

body {
    width: 100vw;
    height: 100vh;
    display: flex;
    align-items: center;
    justify-content: center;
}

.QQ聊天框 {
    width: 600px;
    height: 480px;
    background-color: #eee;
}

.标题部分 {
    height: 38px;
    background-image: linear-gradient(to right, #0D7FFA, #0BD2FA);
    text-align: center;
    line-height: 38px;

    position: relative; /* 坐标系 */
}

.特殊功能区 {
    position: absolute; /* 采用绝对坐标进行布局 */
    height: 38px;
    top: 0;
    right: 10px;
    width: 140px;
    display: flex;
    align-items: center;
    justify-content: space-between;
}

.功能区部分 {
    height: 44px;
    border-bottom: 1px solid #aaa;
}

.主体部分 {
    height: calc(100% - 38px - 44px);
    background-color: #999;
}

.功能区部分 {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 0 8px;
}

.左侧功能区部分 a {
    display: inline-block;
    height: 44px;
    line-height: 44px;
    text-decoration: none;
    color: #888;
}

.左侧功能区部分 a.active {
    border-bottom: 2px solid #000;
    color: #000;
}


.左侧功能区部分 a:hover {
    color: #000;
}

.主体部分 {
    display: flex;
    align-items: stretch;
}

.左侧主体部分 {
    width: 490px;
    display: flex;
    flex-direction: column;
    background-color: yellow;
}

.聊天内容展示区 {
    height: 300px;
    background-color: orange;
}

.聊天输入区 {
    height: calc(100% - 300px);
    background-color: blue;
}

.右侧主体部分 {
    width: calc(100% - 490px);
    background-color: pink;
}